Receiver for wireless signals.



C S FRANKLIN RECEIVER EpR WIRELESS SIGNALS.

- APPLICATION FILED FEB. 26, 19I9- 1,301,246..

Patented'Apr. 22, 1919.

Invavzaor duce oscillations lations 20 d 7 when workin RANKLIN, OFLOIIIDON, ENGLAND, ASSIGNOR T0 a WIRELESS TELEGRAPH COMPANY OF AMERICA,OF NEW YORK, N.

romrron or new mnsmr.

momvanron. Wmmnss SIGNALS. ,24g Specification of Letters Patent.Patented Apr. 252, 1919.

Application med February 28, 1919. Serial No. 279,896.

To all whom it may concern:

Be it known that I, CHARLES SAMUEL FRANKLIN, a subject of the King ofGreat Britain, residing at Marconi House, Strand ndon, England, haveinvented new and useful Improvements in Receivers for Wireless Signals,of which the following. is a specification.

In receivers based on the interference rinciple it is usual to em loy alocal oscilfittOl which can be so ad usted as to prodilfering infrequency by a desired amount from the duced in the receiver by theincoming waves. In some well known receiver's the receiving device isits own local oscillator.

The result is that during reception there are in the receiving circuitstwo sets of modwhich interact with each other, proucing a compoundoscillation of varying amplitude.

The receiver usually rectifies this compound oscillation into auni-directional current of varying strength and so produces in thereceiving telephone a note which has a frequency equal to the differenceof the frequencies of the received and local oscillations, and which cantherefore be, adjusted by varying the frequency of the local oscilaions.

The constancy the constancy of ceived and local oscillations. Forfrequencies below about 1,000,000 per second (300 meter waves) it is notdifiicult to maintain a sufficiently constant frequency; for frequenciesabout 3,000,000 it is still practicable though not easy to maintain asufliciently constant frequency; for frequencies about 30,000,000 it ispracticall impossible to maintain the frequency su ciently constant.

Assuming 30,000,000 to be the frequency received, then -the localoscillator must give a frequency of 30,001,000 or 29,999,000, in orderto give an interference note of 1,000. Should either frequency of oneper cent. the interference note may change; from 1,000 to 4,000.Practically with frequencies of this order the inte erence note variesso rapidly and to such an extent with the small variations of frequencywhich, take place that the signals are dable.

of the note dependsupon oscillations pro audible limits. Th

the frequency of the revary one hundredth According to this invention,the frequency of the local oscillatlons is varied by a small percentage,regularly and in by arranging partly of segments arranged on a rotatingdisk or cylinder, so that the capaclty varies continually between twolimits. receiver constructed according to this invention works asfollows Assume the received frequency to be 30,- 000,000 and the localgenerator arranged to give 30,000,000 frequency with variations of ahalf per cent. above and below this 1,000 times per second. Duringreception an interference note is produced which varies from zero to afrequency of 150,000. An audible sound is produced in the telephone onlyduring the time that the interference note is varying through the rangefrom about 8,000 to zero and back to 8,000; that is to say, while theinterference note is within e period occupied by this range is so shortthat only a click occurs in the telephone for every variation betweenthe above limits of the frequency of the local oscillator. As, however,this variationoccurs 1,000 times per second, a clear note havin afrequency of 1,000 per second is heard w enever signals are received.

receiver for short waves is thus. ob-- tained which has the greatsensitiveness of the interference receiver, but is independent of verysmallvariations in frequency either 1in the received waves or in thelocal oscilator.

The invention is illustrated by the accompos1tio1 1of one of thesegments 6 relative to the strips (1 a and varies mum and minimum as thethe strips.

. Across the coil L is connected a thermionic device at in series with abattery B so arranged as to produce high frequency oscilbetween a maxisegments 6 pass lations in the circuit L C a a in a manner now wellunderstood.

What I claim is 1. In an interference receiving apparatus for wirelesssignals, a circuit containing a generator of local oscillations, andmeans whereby the frequency of said local oscillations is caused to varyregularly and in a continuous manner.

2. In an interference receiving apparatus for wireless signals, anantenna, a circuit associated therewith containing a generator of localoscillations, and means for regularly and in a continuous mannerincreasmg the frequency of the local oscillations above and decreasingthem below the frequency of the received oscillations.

3. In a wireless telegraph receiver, the combination of an aerial, anoscillatory circuit coupled thereto, local means for generating in saidcircuit high frequency oscillations, and means for varying regularly andcontinuously the time period of said circuit.

4. In a wireless tele aph receiver, the combination of an aeria anoscillatory circuit coupled thereto, local means for generatingoscillations in said circuit, and means for varying regularly andcontinuously the frequency of such oscillations.

5. In a wireless telegraph receiver, the combination of an aerial, anoscillatory circuit coupled thereto, local means for generating in saidcircuit high frequency oscillations, and means for varying regularly andcontinuously the'capacity of said circuit.

6. In an interference receiving apparatus for wireless signals, anantenna, a local circuit associated therewith containing a generator ofoscillations, and-means for re larly and continuously vvarying theequency of the local oscillations above and below the limitingfrequencies at which the beats produced by reaction of the received andlocal oscillations are audible, said means being so constructed that thefrequency of said beats passes through the audible range so frequentlyas to produce a distinct note in the receiver corresponding tothe groupfrequency of the audible beats.

CHARLES SAMUEL FRANKLIN.

Witnesses:

Gnoncn J TRUSTY, LEON DE SOUTH.

